Interesting Algorithms

MrAl

Joined Jun 17, 2014
13,704
Ha. Giving scotch tape the moniker of "lens" -- diffusion or otherwise -- is a great offense to actual lenses everywhere!
Hi,

Yeah it is kind of amazing how this works so well. It's like a lot of other stuff we know about though. It's like going backwards through a mixture to 'unmix' it somehow. It depends how much you know about how it was mixed. For these 'lenses', it is assumed that there is some linear transformation at work but we might be able to deviate from that somewhat.

One of the problems though is that digitizing is not a perfect transformation it has serious differences, namely the resolution. If we only had 256 different combinations and the input signal was only between say 200 and 210 for most of the image, we'd end up with a pretty nasty looking output image. Even with today's 16 million color images we see this problem come up when we go to enhance an image. Each color channel has only 8 bits, and that's 256 states. But some images may have all the (say) reds from 150 to 200, which is like 1/5 of the total range. When we go to adjust that, we are already starting with a poor sample. In the analog world, it would not matter as much except for noise. In theory there are an infinite number of levels between 150 and 200, but in the digital world just 50. That's quite a difference. Of course noise messes things up a bit, but that's not always a bad thing.
 

WBahn

Joined Mar 31, 2012
32,844
Not so much an algorithm, but a chain of approaches along with some good explanations of how various historical measurements were (possibly/probably) made.


 
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MrAl

Joined Jun 17, 2014
13,704
Simply awesome.

Hi,

I have his book from back in the early 1970's but not sure when he actually wrote it or did all the many drawings.
The ones I was attracted to most were the 3d to 2d transformations where he takes a 3d object or set of 3d objects and projects them onto a 2d plane, but then that allows more interpretations of the reality so he can show some impossible scenes that look possible in 2d. One example is where people are walking up a staircase and appear to be looping around so they are always walking UP and never down. It's not possible in 3d but in 2d it looks possible.

When I first saw the drawing in the video the first thing I thought of was a transformation because there are a lot of common graphical distortions that are produced by transformations such as punch, skew, cylinder, etc. They all use math transforms to get from the original to the final mostly for special effects. In math though they are used for solving complicated problems that are very hard to solve as first presented. By transforming and solving and then inverse transforming, we get an answer that can be a lot simpler.
The transform in the video is probably z to e^z plus a Mobius transformation. It's amazing that he could come up with this without any complex math (I don't think he used much math but who knows).

One of the things he did not mention for some reason is the preservation of angles in conformal mapping. That's probably one of the most important points. That's why the graphic "little squares" stay little squares, but they actually have to be infinitesimally small in the math.

It is interesting that people are still looking at his work even after all this time. He was pretty amazing and must have had the patience of a god (ha ha). His teacher said he would never become a good architect.
 

WBahn

Joined Mar 31, 2012
32,844
I like this kind of stuff:


Imagine a complete FPU built of nested eml(x,y), and NAND gates.
Looks like much ado about nothing. It's not just "one function", it is a function defined as the sum of two other functions -- so right there you have embedded three functions. exponentiation, logarithm, and addition, By taking two arguments, it makes it pretty straightforward to turn on of the embedded functions off. In one of her examples, she showed applying the additive inverse to one of the arguments, which is yet another operation that is needed/embedded in the system.

I'll take her at face value that this might enable different/new/better ways to explore mathematical structures -- I don't have any basis for having an opinion one way or the other. I also don't have any objection to using things like this to underscore how unified mathematics is at its core.
 

MrAl

Joined Jun 17, 2014
13,704
I like this kind of stuff:


Imagine a complete FPU built of nested eml(x,y), and NAND gates.
Hi,

This 'function' may seem very convoluted at first glance, but because it offers another path to solutions it is very possible and even likely that it could help a lot in theorem proving. I also see a possibility for using it for function searching using an evolutionary type strategy. As quantum computers evolve, it may become even more important.

Part of the key point would be how fast does it work versus using a regular set of functions we normally see, and can we really build ANY function from this or will there be functions that come up that can't be found with this idea. It's an interesting concept though I might have to explore it a little myself.

It does look like some of the higher functions even sin and cos might involve several steps though. That could increase computation time on a regular computer. Note she did not show how to get sin or cos.

This might go pretty high up on the list of "interesting functions" though regardless.
 
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